I've been struggling with the concept of having simple, easy to use packages for pretty much everyone out there, and at the same time have the flexibility to do crazy advanced things like have four different versions of postgres or mysql on a system at once. For most people, they want a simple desktop or simple server machine and want upgrades to be as easy and seemless as possible. If there's a safe way to upgrade postgres 7.2 to 8.1 then that's what I want to happen. But in some cases you need both.